/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Collection;
import java.util.Comparator;
import java.util.NavigableMap;
import java.util.NavigableSet;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;
import javax.annotation.Nullable;

/**
 * Implementation of {@code Multimap} whose keys and values are ordered by their natural ordering or
 * by supplied comparators. In all cases, this implementation uses {@link Comparable#compareTo} or
 * {@link Comparator#compare} instead of {@link Object#equals} to determine equivalence of
 * instances.
 *
 * <p>
 * <b>Warning:</b> The comparators or comparables used must be <i>consistent with equals</i> as
 * explained by the {@link Comparable} class specification. Otherwise, the resulting multiset will
 * violate the general contract of {@link SetMultimap}, which it is specified in terms of
 * {@link Object#equals}.
 *
 * <p>
 * The collections returned by {@code keySet} and {@code asMap} iterate through the keys according
 * to the key comparator ordering or the natural ordering of the keys. Similarly, {@code get},
 * {@code removeAll}, and {@code
 * replaceValues} return collections that iterate through the values according to the value
 * comparator ordering or the natural ordering of the values. The collections generated by
 * {@code entries}, {@code keys}, and {@code values} iterate across the keys according to the above
 * key ordering, and for each key they iterate across the values according to the value ordering.
 *
 * <p>
 * The multimap does not store duplicate key-value pairs. Adding a new key-value pair equal to an
 * existing key-value pair has no effect.
 *
 * <p>
 * Null keys and values are permitted (provided, of course, that the respective comparators support
 * them). All optional multimap methods are supported, and all returned views are modifiable.
 *
 * <p>
 * This class is not threadsafe when any concurrent operations update the multimap. Concurrent read
 * operations will work correctly. To allow concurrent update operations, wrap your multimap with a
 * call to {@link Multimaps#synchronizedSortedSetMultimap}.
 *
 * <p>
 * See the Guava User Guide article on
 * <a href= "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multimap">
 * {@code Multimap}</a>.
 *
 * @author Jared Levy
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible(serializable = true, emulated = true)
public class TreeMultimap<K, V> extends AbstractSortedKeySortedSetMultimap<K, V> {
    private transient Comparator<? super K> keyComparator;
    private transient Comparator<? super V> valueComparator;

    /**
     * Creates an empty {@code TreeMultimap} ordered by the natural ordering of its keys and values.
     */
    public static <K extends Comparable, V extends Comparable> TreeMultimap<K, V> create() {
        return new TreeMultimap<K, V>(Ordering.natural(), Ordering.natural());
    }

    /**
     * Creates an empty {@code TreeMultimap} instance using explicit comparators. Neither comparator
     * may be null; use {@link Ordering#natural()} to specify natural order.
     *
     * @param keyComparator the comparator that determines the key ordering
     * @param valueComparator the comparator that determines the value ordering
     */
    public static <K, V> TreeMultimap<K, V> create(Comparator<? super K> keyComparator,
            Comparator<? super V> valueComparator) {
        return new TreeMultimap<K, V>(checkNotNull(keyComparator), checkNotNull(valueComparator));
    }

    /**
     * Constructs a {@code TreeMultimap}, ordered by the natural ordering of its keys and values,
     * with the same mappings as the specified multimap.
     *
     * @param multimap the multimap whose contents are copied to this multimap
     */
    public static <K extends Comparable, V extends Comparable> TreeMultimap<K, V> create(
            Multimap<? extends K, ? extends V> multimap) {
        return new TreeMultimap<K, V>(Ordering.natural(), Ordering.natural(), multimap);
    }

    TreeMultimap(Comparator<? super K> keyComparator, Comparator<? super V> valueComparator) {
        super(new TreeMap<K, Collection<V>>(keyComparator));
        this.keyComparator = keyComparator;
        this.valueComparator = valueComparator;
    }

    private TreeMultimap(Comparator<? super K> keyComparator, Comparator<? super V> valueComparator,
            Multimap<? extends K, ? extends V> multimap) {
        this(keyComparator, valueComparator);
        putAll(multimap);
    }

    /**
     * {@inheritDoc}
     *
     * <p>
     * Creates an empty {@code TreeSet} for a collection of values for one key.
     *
     * @return a new {@code TreeSet} containing a collection of values for one key
     */
    @Override
    SortedSet<V> createCollection() {
        return new TreeSet<V>(valueComparator);
    }

    @Override
    Collection<V> createCollection(@Nullable K key) {
        if (key == null) {
            keyComparator().compare(key, key);
        }
        return super.createCollection(key);
    }

    /**
     * Returns the comparator that orders the multimap keys.
     *
     * @deprecated Use {@code ((NavigableSet<K>) multimap.keySet()).comparator()} instead. This
     *             method is scheduled for removal in April 2019.
     */
    @Deprecated
    public Comparator<? super K> keyComparator() {
        return keyComparator;
    }

    @Override
    public Comparator<? super V> valueComparator() {
        return valueComparator;
    }

    /**
     * @since 14.0 (present with return type {@code SortedSet} since 2.0)
     */
    @Override
    @GwtIncompatible // NavigableSet
    public NavigableSet<V> get(@Nullable K key) {
        return (NavigableSet<V>) super.get(key);
    }

    /**
     * {@inheritDoc}
     *
     * <p>
     * Because a {@code TreeMultimap} has unique sorted keys, this method returns a
     * {@link NavigableSet}, instead of the {@link java.util.Set} specified in the {@link Multimap}
     * interface.
     *
     * @since 14.0 (present with return type {@code SortedSet} since 2.0)
     */
    @Override
    public NavigableSet<K> keySet() {
        return (NavigableSet<K>) super.keySet();
    }

    /**
     * {@inheritDoc}
     *
     * <p>
     * Because a {@code TreeMultimap} has unique sorted keys, this method returns a
     * {@link NavigableMap}, instead of the {@link java.util.Map} specified in the {@link Multimap}
     * interface.
     *
     * @since 14.0 (present with return type {@code SortedMap} since 2.0)
     */
    @Override
    public NavigableMap<K, Collection<V>> asMap() {
        return (NavigableMap<K, Collection<V>>) super.asMap();
    }

    /**
     * @serialData key comparator, value comparator, number of distinct keys, and then for each
     *             distinct key: the key, number of values for that key, and key values
     */
    @GwtIncompatible // java.io.ObjectOutputStream
    private void writeObject(ObjectOutputStream stream) throws IOException {
        stream.defaultWriteObject();
        stream.writeObject(keyComparator());
        stream.writeObject(valueComparator());
        Serialization.writeMultimap(this, stream);
    }

    @GwtIncompatible // java.io.ObjectInputStream
    @SuppressWarnings("unchecked") // reading data stored by writeObject
    private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
        stream.defaultReadObject();
        keyComparator = checkNotNull((Comparator<? super K>) stream.readObject());
        valueComparator = checkNotNull((Comparator<? super V>) stream.readObject());
        setMap(new TreeMap<K, Collection<V>>(keyComparator));
        Serialization.populateMultimap(this, stream);
    }

    @GwtIncompatible // not needed in emulated source
    private static final long serialVersionUID = 0;
}
